Citizenship ceremonies are for adults whose application to become a British citizen has been accepted and it is a legal requirement that the applicant takes a citizenship pledge and an oath of allegiance at a citizenship ceremony, within 90 days of the applicant receiving their invitation.
Group sizes vary from 15 to 25 people, and each applicant can bring 2 guests. for further information – http://www.kent.gov.uk/births-ceremonies-and-deaths/other-ceremonies/citizenship-ceremony